FN makes barrels for the US military, and supplies both M4 and M16 rifles to the military. FN is one of the premier manufacturers of military spec barrels. This barrel is button broached, as is military spec and used by FN, Colt, LMT and other military providers. Featuring the military standard 1:7 twist and chambered in 5.56 NATO, fully chrome-lined and the standard carbine gas system and M4 feedramps, this barrel is ready for your URGi build or any AR / M4 / M16 style rifle, either as an upgrade or a new build.
FN replacement part number 20-100046
Note: Charlie's also sells the FN button rifle cut 16" barrel in mid-length gas system: FN 16" midlength chrome-lined button rifled barrel The difference between these two barrels is the gas system, or where the gas port is. The carbine gas system is shorter and more common in military barrel. The mid-length system is somewhat of a newer design. Typically, the US military uses FN button rifled barrels, and historically, has used the carbine gas system. Newer barrels are migrating in the 14.5" and longer to mid-length, but both are common.